a person is asked to pass urine and a final X-ray is taken. Before the test, a person is asked to pass urine so that their bladder is emptied. They are asked to lie flat during the procedure. Normal appearances Immediately after the contrast is administered, it appears on an X-ray as a 'renal blush'. This is the contrast being filtered through the cortex. At an interval of 3 minutes, the renal blush is still evident (to a lesser extent) but the calyces and renal pelvis are now visible. At 9 to 13 minutes the contrast begins to empty into the ureters and travel to the bladder which has now begun to fill. To visualize the bladder correctly, a post micturition X-ray is taken, so that the bulk of the contrast (which can mask a pathology) is emptied. An IVP can be performed in either emergency or routine circumstances. Emergency IVP This procedure is carried out on patients who present to an Emergency department, usually with severe renal colic and a positive hematuria test. In this circumstance the attending physician requires to know whether a patient has a kidney stone and if it is causing any obstruction in the urinary system. Patients with a positive find for kidney stones but with no obstruction are sometimes discharged based on the size of the stone with a follow-up appointment with a urologist. Patients with a kidney stone and obstruction are usually required to stay in hospital for monitoring or further treatment. An Emergency IVP is carried out roughly as follows: plain KUB or abdominal X-ray; an injection of contrast media, typically 50 ml; delayed abdominal X-ray, taken at roughly 15 minutes post injection. If no obstruction is evident on this film a post-micturition film is taken and the patient is sent back to the Emergency department. If an obstruction is visible, a post-micturition film is still taken, but is followed up with a series of radiographs taken at a "double time" interval. For example, at 30 minutes post-injection, 1 hour, 2 hours, 4 hours, and so forth, until the obstruction is seen to resolve.This is useful because this time delay can give important information to the urologist on where and how severe the obstruction is. Routine IVP This procedure is most common for patients who have unexplained microscopic or macroscopic hematuria. It is used to ascertain the presence of a tumour or